AC grounding questions

The purpose of having grounding pin on AC outlet is to ground metalic
surfaces of appliances so that there can be no voltage to hurt anyone even
if there is a leak. Right?
If an AC outlet has the ground and neutral reversed, would it cause any
problem?
If an AC outlet has no grounding wire (old house) and instead the ground
prong is connected to the neutral, would that cause any problem?
Is neutral connected to ground at the circult breaker panel?

Right.
If the neutral is shared with another outlet, there is the very real
possibility of voltage being on it.

Yes, then the metal surfaces of the appliance would be subject to
voltage.

Yes, but that does not mean they are interchangeable in usage at the
outlet end. It is to insure that the breakers trip if the hot line is
shorted out to ground and not just the other side of the power line.
--
If I had something witty to say, this is where I'd say it.

I remember taking awhile to understand the difference between neutral
and ground (connected at the panel). Neutral can be at a different
voltage because of current on it. The ground wire normally doesn't
carry current and should be at 0V.
Also, it's unsafe to have ground connected to other receptacle(s) but
not the panel (as someone who thinks a GFCI actually provides ground
might do).

To be more specific, when you return current to the utility via the neutral
conductor, there will be a voltage drop along that path proportional to the
resistance of that conductor. If a failure or resistive connection
develops, that voltage could be quite high (closer to the hot V).
This voltage drop on the neutral is expected and most electricians will
avoid touching the white wire as well as the black. The ground (AKA Safety
Ground, not earth ground) is just a parallel connection which normally does
not have much current flowing on it and thus does not have an expected
voltage drop when a load is connected unless there is a leakage fault.
Much of the grounding system is not needed if everything is perfect but
since things do fail, this is why it is here.

I've seen in the codes something about window units having voltage
leakage detectors on them. So many people have screwed with the
ground wire in the past, they killed themselves adjusting the AC unit.
Touch a unit, with an open neutral and a radiator, and get fried kind
of stories I've heard.
So, I would get it fixed, reguardless if it works.
imho,
tom @ www.NoCostAds.com

Besides what others mention you need to find out your houses
efficiency, a Blower Door test is good it tells you how many air
exchanges your house has and shows you where it leaks. Your attic is
under insulated.

Only at the main service panel - not at a subpanel...
...unless a grounding rod is required, as in a separate building,
then the bonding screw is used at that subpanel.
Also, in the US, neutral grounds are sometimes legal, with major
appliances on a dedicated circuit. Or at least they were. Existing 3
wire 120-240 circuits are still allowed to remain, but new
construction requires a 4 wire connection to things like electric
ranges and clothes dryers. No more neutral grounding allowed.
I can't remember exactly when the NEC made these changes.
I think it was 1996. Correct me if I'm wrong. Existing
hookups are grandfathered, however, as long as there is no
remodel/new construction.

What would happen if (intentionally) the service didn't use a grounded
neutral at all? Everything the same but don't ground the neutral at the
transformer nor at the consumer's entrance panel. Would that make things
more dangerous or reduce shock hazard because you could only get a shock if
you bridged two conductors?

Lightning? Hardly.
When lightning zaps a circuit, it flows common-mode, down all three
conductors. It WILL find a path to ground.
Six million volts is brutal by nature. <g>
A few hundred gigawatts doesn't take very long to toast anything
in its path.

The danger would be that the voltage to ground would be uncontrolled. Any
leakage or accidental connection from the transformer primary could raise
both sides of the house wiring to the primary voltage, which could be
several thousand volts. Definitely more dangerous.
Don Young

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